CVE-2026-8821

published 2026-09-14

CVE-2026-8821: Mattermost versions 11.9.x <= 11.9.0, 11.8.x <= 11.8.4, 11.7.x <= 11.7.7, 10.11.x <= 10.11.22 fail to validate channel member-management permission during…

Priority P3 44 high 7.1 CVSS 3.1

AV N AC L PR L UI N S U C H I L A N

Mattermost versions 11.9.x <= 11.9.0, 11.8.x <= 11.8.4, 11.7.x <= 11.7.7, 10.11.x <= 10.11.22 fail to validate channel member-management permission during playbook run creation, allowing an authenticated channel member to add an arbitrary user to a restricted channel via the run owner field.. Mattermost Advisory ID: MMSA-2026-00677

Affected

8 ranges

Vendor	Product	Version range	Fixed in
mattermost	mattermost	10.11.0 – 10.11.22	—
mattermost	mattermost	11.7.0 – 11.7.7	—
mattermost	mattermost	11.8.0 – 11.8.4	—
mattermost	mattermost	11.9.0 – 11.9.0	—
mattermost	mattermost_server	>= 10.11.0 < 10.11.23	10.11.23
mattermost	mattermost_server	>= 11.7.0 < 11.7.8	11.7.8
mattermost	mattermost_server	>= 11.8.0 < 11.8.5	11.8.5
mattermost	mattermost_server	>= 11.9.0 < 11.9.1	11.9.1

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CWE-862